Secondary Metabolites of Biscogniauxia: Distribution, Chemical Diversity, Bioactivity, and Implications of the Occurrence

The genus Biscogniauxia, a member of the family Xylariaceae, is distributed worldwide with more than 50 recognized taxa. Biscogniauxia species is known as a plant pathogen, typically acting as a parasite on tree bark, although certain members of this genus also function as endophytic microorganisms. Biscogniauxia endophytic strain has received attention in many cases, which includes constituent research leading to the discovery of various bioactive secondary metabolites. Currently, there are a total of 115 chemical compounds belonging to the class of secondary metabolites, and among these compounds, fatty acids have been identified. In addition, the strong pharmacological agents of this genus are (3aS,4aR,8aS,9aR)-3a-hydroxy-8a-methyl-3,5-dimethylenedecahydronaphto [2,3-b]furan-2(3H)-one (HDFO) (antifungal), biscopyran (phytotoxic activity), reticulol (antioxidant), biscogniazaphilone A and B (antimycobacterial), and biscogniauxone (Enzyme GSK3 inhibitor). This comprehensive research contributes significantly to the potential discovery of novel drugs produced by Biscogniauxia and holds promise for future development. Importantly, it represents the first-ever review of natural products originating from the Biscogniauxia genus.


Introduction
A significant variety of natural products have been isolated and identified from many fungi, consisting of approximately 47% of the roughly 33,500 bioactive microbial metabolites [1].Endophytic fungi are organisms that live in plant tissues without causing harm and produce biologically active compounds specific to the host plants [2].They are considered a potential source of new bioactive natural material for new drug development, inhabiting the inner tissues of living plants [3,4].Some endophytic fungi can produce the same or similar bioactive substances as those found in the host plant, one of which is the genus Biscogniauxia [5].
Biscogniauxia is a genus of fungi in the family Xylariaceae with more than 50 recognized taxa worldwide [6,7].Biscogniauxia endophytic strain has received attention in many cases, which includes constituent research leading to the discovery of various bioactive secondary metabolites [4].Since the first report on the secondary metabolites of Biscogniauxia in 2005,

Azaphilone Derivatives
A new azaphilone derivative was successfully isolated from the n-BuOH soluble fraction of 95% EtOH extract from substrate culture on B. formosana to produce Biscogniazaphilones A (1) and Biscogniazaphilones B (2) [10] (Figure 1).This marks the first report of this compound being isolated from B. formosana.Subsequently, azaphilones or azaphilonoids are fungal polyketides known for the highly oxygenated cyclic pyranoquinone core, usually referred to as isochromenes and quaternary carbon centers, and also known as pigments [24,25].Compounds 1 and 2 based on the spectra of 1 H NMR and 13 C NMR are similar, but compound 2 has one γ-lactone group between C-6a and C-9.

Azaphilone Derivatives
A new azaphilone derivative was successfully isolated from the n-BuOH solubl tion of 95% EtOH extract from substrate culture on B. formosana to produce B niazaphilones A (1) and Biscogniazaphilones B (2) [10] (Figure 1).This marks the fi port of this compound being isolated from B. formosana.Subsequently, azaphilon azaphilonoids are fungal polyketides known for the highly oxygenated cyclic pyran none core, usually referred to as isochromenes and quaternary carbon centers, and known as pigments [24,25].Compounds 1 and 2 based on the spectra of 1 H NMR an NMR are similar, but compound 2 has one γ-lactone group between C-6a and C-9.

Cerebrosides
Cerebrosides are a family of glycosphingolipids and important components of various tissues and organs in biological systems.Chemically, cerebrosides consist of hexose and ceramide groups, typically consisting of long-chain amino alcohols commonly called "sphingoid bases" (=sphingosine or sphingol) and amide-linked long-chain fatty acids [26].While cerebrosides can be found in plants, fungi, and animals, distinct variations exist in the structure of the ceramide backbone among these organisms [27].In the genus Biscogniauxia, Cerebroside A (3) and Cerebroside C (4) (Figure 2) were successfully isolated from the ethyl acetate extract in the stroma of Biscogniauxia whalleyi mushrooms cultivated on potato dextrose agar (PDA) media.Fungal cerebrosides exhibited remarkable structural conservation, with modifications including different unsaturation sites as well as varying lengths of fatty acid residues in the ceramide moiety [28].

Coumarin
Coumarin is a secondary metabolite derived from 1,2 benzopyrone, formed from the benzene ring, and α-pyrone found in microorganisms and higher plants, originating from the phenylpropanoid pathway [29,30].Coumarin has been extensively examined as one of the most promising structures for the development of new agents with higher specificity and affinity against molecular targets.Furthermore, it is characterized by its intrinsic properties such as antimicrobial, antioxidant, anti-inflammatory, antiadipogenic, cytotoxic, apoptotic, antiproliferative, antimycobacterial activity against Mycobacterium tuberculosis, antileishmanial, antiviral, anticancer, and cytotoxic agent [31].Biscogniauxia endophytic strain has garnered attention in constituent research, leading to the discovery of various bioactive secondary metabolites, specifically in the context of coumarins.Given their wide range of pharmacological values, coumarins and their derivatives hold significant importance in synthesis and production.The coumarin is produced from Biscogniauxia and is divided into three groups: coumarin compounds 5-7, isocoumarins 8-9, and dihydroisocoumarin (Melleins) compounds 10-25 (Figure 3). (2).

Cerebrosides
Cerebrosides are a family of glycosphingolipids and important components of various tissues and organs in biological systems.Chemically, cerebrosides consist of hexose and ceramide groups, typically consisting of long-chain amino alcohols commonly called "sphingoid bases" (=sphingosine or sphingol) and amide-linked long-chain fatty acids [26].While cerebrosides can be found in plants, fungi, and animals, distinct variations exist in the structure of the ceramide backbone among these organisms [27].In the genus Biscogniauxia, Cerebroside A (3) and Cerebroside C (4) (Figure 2) were successfully isolated from the ethyl acetate extract in the stroma of Biscogniauxia whalleyi mushrooms cultivated on potato dextrose agar (PDA) media.Fungal cerebrosides exhibited remarkable structural conservation, with modifications including different unsaturation sites as well as varying lengths of fatty acid residues in the ceramide moiety [28].

Fatty Acids
From the Biscogniauxia endophytic strain, one fatty acid that was effectively isolated was linoleic acid (26), obtained in the form of a colorless oil.This isolation was achieved from the EtOAc-soluble fraction of a 95% EtOH rice extract that underwent fermentation

Fatty Acids
From the Biscogniauxia endophytic strain, one fatty acid that was effectively isolated was linoleic acid (26), obtained in the form of a colorless oil.This isolation was achieved from the EtOAc-soluble fraction of a 95% EtOH rice extract that underwent fermentation with B. cylindrospora [4] (Figure 5).

Fatty Acids
From the Biscogniauxia endophytic strain, one fatty acid that was effectively isolated was linoleic acid (26), obtained in the form of a colorless oil.This isolation was achieved from the EtOAc-soluble fraction of a 95% EtOH rice extract that underwent fermentation with B. cylindrospora [4] (Figure 5).

Fatty Acids
From the Biscogniauxia endophytic strain, one fatty acid that was effectively was linoleic acid (26), obtained in the form of a colorless oil.This isolation was a from the EtOAc-soluble fraction of a 95% EtOH rice extract that underwent ferm with B. cylindrospora [4] (Figure 5).

Hydroxycinnamic Acids and Derivatives
In the category of hydroxycinnamic acids and derivatives, after a series o stages, dried rice from B. formosana BCRC 33718 was extracted with 95% EtOH an to preparative TLC using MeOH as a developer.This process yielded N-trans-fe methyl-dopamine (29), the sole compound in the hydroxycinnamic acids and group.This compound had previously been identified in spinach leaves (Spina [36] (Figure 8).

Hydroxycinnamic Acids and Derivatives
In the category of hydroxycinnamic acids and derivatives, after a series of isolation stages, dried rice from B. formosana BCRC 33718 was extracted with 95% EtOH and subjected to preparative TLC using MeOH as a developer.This process yielded N-trans-feruloy-3-Omethyl-dopamine (29), the sole compound in the hydroxycinnamic acids and derivatives group.This compound had previously been identified in spinach leaves (Spinacia oleracea) [36] (Figure 8).
In the category of hydroxycinnamic acids and derivatives, after a series of isolation stages, dried rice from B. formosana BCRC 33718 was extracted with 95% EtOH and subjected to preparative TLC using MeOH as a developer.This process yielded N-trans-feruloy-3-Omethyl-dopamine (29), the sole compound in the hydroxycinnamic acids and derivatives group.This compound had previously been identified in spinach leaves (Spinacia oleracea) [36] (Figure 8).
In the category of hydroxycinnamic acids and derivatives, after a series of isolation stages, dried rice from B. formosana BCRC 33718 was extracted with 95% EtOH and subjected to preparative TLC using MeOH as a developer.This process yielded N-trans-feruloy-3-Omethyl-dopamine (29), the sole compound in the hydroxycinnamic acids and derivatives group.This compound had previously been identified in spinach leaves (Spinacia oleracea) [36] (Figure 8).

Naphthoquinones
Naphthoquinones are widespread and have been found in higher plants, fungi, and actinomycetes [38].In the extract of B. mediterranea strain LF657, isolated from deep-sea sediments in the eastern Mediterranean Sea at a water depth of 2800 m, the new isopyrrolonaphthoquinone compound naphtho [2,3]furandione (isofuranonaphthoquinone) (biscogniauxone) (33) was identified [17] (Figure 10).Many researchers have an interest in this class of naphthoquinone compounds because of their wide range of biological activities, such as phytotoxic, insecticidal, antibacterial, and fungicide.In addition, some of these compounds also have cytostatic [39] and anticarcinogenic properties [38].As for compound (33), it shows inhibitory activity against the GSK-3β enzyme [17], which will be explained further in Section 3. Naphthoquinones are widespread and have been found in higher plants, fungi, and actinomycetes [38].In the extract of B. mediterranea strain LF657, isolated from deep-sea sediments in the eastern Mediterranean Sea at a water depth of 2800 m, the new isopyrrolonaphthoquinone compound naphtho [2,3]furandione (isofuranonaphthoquinone) (biscogniauxone) (33) was identified [17] (Figure 10).Many researchers have an interest in this class of naphthoquinone compounds because of their wide range of biological activities, such as phytotoxic, insecticidal, antibacterial, and fungicide.In addition, some of these compounds also have cytostatic [39] and anticarcinogenic properties [38].As for compound (33), it shows inhibitory activity against the GSK-3β enzyme [17], which will be explained further in Section 3.

Steroids
Steroids play a crucial role in the active ingredients of medicines found across the animal and plant kingdoms, characterized by a common chemical framework of four fused rings, including three six-membered rings and a five-membered ring [56].Several steroids are produced from the genus Biscogniauxia, including B. whalleyi, B. formosana, and B. cylindrospora.In the n-BuOH soluble fraction, a 95% EtOH extract of long grain rice produced by the endophytic fungus B. formosana BCRC 33718 was fractionated with a combination of silica gel, RP-18 column, and preparative TLC to produce 12 compounds, and one of them was a steroid group, namely ergosta-4,6,8( 14),22-tetraen-3-one (64) [10], which was previously isolated from Ganoderma applanatum [57].Furthermore, 4 steroid compounds were also isolated from B. whalleyi based on data from intensive comparisons of NMR data, specific optical rotation values, and MS data with those in the literature,

Steroids
Steroids play a crucial role in the active ingredients of medicines found across the animal and plant kingdoms, characterized by a common chemical framework of four fused rings, including three six-membered rings and a five-membered ring [56].Several steroids are produced from the genus Biscogniauxia, including B. whalleyi, B. formosana, and B. cylindrospora.In the n-BuOH soluble fraction, a 95% EtOH extract of long grain rice produced by the endophytic fungus B. formosana BCRC 33718 was fractionated with a combination of silica gel, RP-18 column, and preparative TLC to produce 12 compounds, and one of them was a steroid group, namely ergosta-4,6,8( 14),22-tetraen-3-one (64) [10], which was previously isolated from Ganoderma applanatum [57].Furthermore, 4 steroid compounds were also isolated from B. whalleyi based on data from intensive comparisons of NMR data, specific optical rotation values, and MS data with those in the literature, indicating that the isolated compound were cerevisterol (62) [58], ergone (63) [59], ergosterol (65) [58], and ergosterol peroxide (66) [60] (Figure 17).Three steroid compounds were also isolated from B. cylindrospora, namely 3β-hydroxystigmast-5-en-7-one (67), which was produced in rice from B. cylindrospora BCRC 33717, then extracted three times with 70% EtOH at room temperature [15] and two steroids, β-sitostenone (68) and β-sitosterol (69), in the EtOAc soluble fraction of B. cylindrospora BCRC 33717 [4] (Figure 17).[19].Subsequently, diterpenoids are natural compounds with a C-20 carbon skeleton that are chemically heterogeneous.They are widely distributed from the condensation of four isoprene units derived from the mevalonate or deoxysylulose phosphate pathway.Diterpenoids can be classified as linear, bicyclic, tricyclic, tetracyclic, pentacyclic, or macrocyclic diterpenes, depending on their core framework.In nature, they are generally found in polyoxygenated forms with keto and hydroxyl groups, which are often esterified by small aliphatic or aromatic acids [61].Biscognisecoisopimarate A (70) was obtained as colorless needle crystals, while 3β-hydroxyrickitin A (71) (Figure 18) was obtained as a yellowish oil, which was then tested for its biological activity for anti-Alzheimer disease (AD) activity, anti-inflammatory, and cytotoxic activity [20], which will be discussed further in Section 2.
Toxins 2023, 15, x FOR PEER REVIEW 15 of 26 (Figure 18) was obtained as a yellowish oil, which was then tested for its biological activity for anti-Alzheimer disease (AD) activity, anti-inflammatory, and cytotoxic activity [20], which will be discussed further in Section 2.  70) and ( 71).

Sesquiterpenoids
Sesquiterpenoids are derived from three isoprene units and exist in various forms, including linear, monocyclic, bicyclic, and tricyclic frameworks.They are the most diverse group of terpenoids [63].Seven new sesquiterpenoids of the guanine type, namely biscogniauxiaol A-G (90-96), were successfully isolated from the endophytic fungus Biscog-

Other
Meso-2,3-butanediol (115) is the only phytotoxin isolated from Biscogniauxia rosacearum (IRAN 4194C) (Figure 24).This compound was first identified as a pathogen included in GTD in the Paveh vineyard, Kermanshah Province (west of Iran) [14].This compound showed no optical activity and was identified based on spectroscopic data, as reported by Gallwey et al., 1990 [79].

Biological Activity
Mushrooms, including various fungal species, are a valuable source of numerous sec-

Other
Meso-2,3-butanediol (115) is the only phytotoxin isolated from Biscogniauxia rosacearum (IRAN 4194C) (Figure 24).This compound was first identified as a pathogen included in GTD in the Paveh vineyard, Kermanshah Province (west of Iran) [14].This compound showed no optical activity and was identified based on spectroscopic data, as reported by Gallwey et al., 1990 [79].

Biological Activity
Mushrooms, including various fungal species, are a valuable source of numerous secondary metabolites with diverse chemical structures and a wide range of biological activi-

Other
Meso-2,3-butanediol (115) is the only phytotoxin isolated from Biscogniauxia rosacearum (IRAN 4194C) (Figure 24).This compound was first identified as a pathogen included in GTD in the Paveh vineyard, Kermanshah Province (west of Iran) [14].This compound showed no optical activity and was identified based on spectroscopic data, as reported by Gallwey et al., 1990 [79].

Other
Meso-2,3-butanediol (115) is the only phytotoxin isolated from Biscogniauxia rosacearum (IRAN 4194C) (Figure 24).This compound was first identified as a pathogen included in GTD in the Paveh vineyard, Kermanshah Province (west of Iran) [14].This compound showed no optical activity and was identified based on spectroscopic data, as reported by Gallwey et al., 1990 [79].

Biological Activity
Mushrooms, including various fungal species, are a valuable source of numerous secondary metabolites with diverse chemical structures and a wide range of biological activi-

Biological Activity
Mushrooms, including various fungal species, are a valuable source of numerous secondary metabolites with diverse chemical structures and a wide range of biological activities [25,80].Fungi, in general, have well-developed secondary metabolic pathways, and the sheer diversity of fungal species and the biosynthetic gene pools suggest a nearly limitless potential for metabolic variation.This diversity serves as an untapped resource for drug discovery and synthetic biology [1].Among these fungi, one of the fungal species that is rich in biologically active secondary metabolites is endophytic fungi [81].They are found on a variety of plant hosts, ranging from herbaceous plants in a variety of habitats, including extreme arctic, alpine, and xeric environments, to subtropical and mesic tropical forests [82].Subsequently, nearly 300,000 plant species on Earth host one or more endophytics [83], and one such endophytic is the Biscogniauxia endophytic strain.Currently, secondary metabolites from Biscogniauxia show a variety of biological activities and have become important candidates for the development of new drugs, which are summarized in Table 2.

Antioxidants
Endophytic fungi have gained attention as an alternative source of these valuable compounds due to their potential health benefits [87].Subsequently, B. capnodes isolated from the fruit of Averrhoa carambola L. (Oxalidaceae), commonly called starfruit, has been found to produce compounds of the isocumarin and dihydroisocoumarin groups.These compounds include 6-O-methyl-reticulol (8), reticulol (9), 7-hydroxy-5-methylmellein (15), and 5-methylmellein (21) [21].Among these compounds, reticulol (9) exhibited significant DPPH radical scavenging activity with an IC 50 value of 58 µg/mL (IC 50 of the positive control butylated hydroxyanisole was 5.5 µg/mL) [12].These compounds are believed to have a strong protective mechanism against the generation of free radicals, which cause several disorders such as aging, cancer, atherosclerosis, coronary heart disease, and diabetes.Reticulol exhibits moderate antioxidant activity; this compound was first discovered in a strain of Streptomyces rubrireliculae [88].It has been widely reported to have other biological activities, such as its antitumor properties by deactivating Topo I, which is included in tumor metastasis, and exhibiting excellent cytotoxicity against melanoma B16F10 when combined with adriamycin [89].Additionally, it serves as an inhibitor of cyclic adenosine 3 ,5 -monophosphate phosphodiesterase [79] and cyclic nucleotide phosphodiesterase [90].Recent research showed its ability to significantly reduce degranulation and histamine release [91].

Antigerminative
The fungus isolated as an endophytic from the plum yew Cephalotaxus harringtonia, namely the B. nummularia strain, was subjected to a chromatography technique to produce chemical constituents, which were then tested for anti-germinative activity to determine any suspected phytopathogenesis.The anti-germinative tests were carried out using radish seeds, with all compounds tested at a maximum concentration of 100 mg/mL, which is comparable to the effective concentration of glyphosate, a commonly used weed killer constituent.Among the compounds tested, xylaranone (104) exhibited the strongest antigerminative activity with an 85% inhibition rate, surpassing the reference glyphosate (75% inhibition).Xylaranol B also showed significant effectiveness against seed germination, with over 50% inhibition at the tested concentrations.Meanwhile, compounds derived from mellein, namely compounds 10 and 11, had inhibitory effects of less than 50% [13].

Phytotoxic Activity
Phytotoxins are bioactive substances produced naturally by various plants and microbial species (e.g., bacteria and fungi), some of which can be consumed by humans [92].Fungal phytotoxins, also known as phytotoxic secondary metabolites from fungi, are substances that are naturally produced by fungi through biochemical reactions, and they have toxic effects on plants [93].Fungal phytotoxins play an important role in the development of plant disease symptoms, including leaf spot, wilting, chlorosis, and necrosis, as well as growth inhibition and enhancement [94].Biscogniauxia rosacearum, first recognized as a pathogen causing grape stem disease in Paveh vineyards (western Iran), produces meso-2,3butanediol (115).(3R)-5-methylmellein (22), (3R)-5-methyl-6-methoxymellein (23), tyrosol (47).In addition, nectriapyrone (59) was produced as a phytotoxin from the same fungal strain isolated from oak trees in the Zagros forest in Gilan-e Gharb, Kermanshah Province.The phytotoxicity of secondary metabolites of B. rosacearum was tested by leaf pricking on Quercus ilex L. and Hedera helix L. and by foliar absorption tests on grapevine (Vitis vinifera L.) at concentrations of 5 × 10 −3 and 10 −3 M.Among these compounds, 22 and 115 were found to be the most phytotoxic on grapevine.In the case of Q. ilex, compounds 46 and 58 induced severe necrosis at the highest concentration, while none of the compounds exhibited activity on H. helix [14].

Activity against the Enzyme GSK-3β
The production of bioactive compounds, specifically those with parasitic pathogenic properties or phytotoxic substances, has been extensively examined in various Bioscogniauxia strains.One of these strains, Bioscogniauxia mediterranea strain LF657, which was isolated from deep-sea sediments of the East Mediterranean Sea at a water depth of 2800 m, produces a new compound identified as the isopyrrolonaphthoquinone group, namely biscogniauxone (33) showing activity that inhibits glycogen synthase kinase GSK-3β with an IC 50 value of 8.04 µM (±0.28) [17].In another investigation, the compound bhimamycin H, the isopyrrolonaphthoquinone group, also inhibited the activity of this enzyme in the same range (IC 50 value 18 µM) [95].Therefore, isopyrrolonaphthoquinones and similar structures can be considered potential candidates for drug development to treat diseases associated with GSK-3β biological targets, such as type 2 diabetes, neurological disorders, or cancer [96][97][98].

Anti-Acetylcholinesterase (AChE) Activity and Anti-Alzheimer Disease (AD)
AD is the leading cause of dementia, contributing to approximately 75% of all dementia cases.The pathophysiological processes described for the development of AD include neuronal and synaptic degeneration, characterized mainly by cholinergic disturbances.As a result, AChE inhibitors represent the primary class of drugs used in the treatment of the dementia phase of AD [99].Several investigations have explored the search for natural molecules with AChE inhibitory properties.These investigations have examined various compounds, particularly those falling into categories such as alkaloids, monoterpenes, coumarins, triterpenes, flavonoids, benzenoids, diterpenes, heterocyclic oxygen, sesquiterpenes, stilbenes, lignans, sulfur compounds, proteinids, polycyclics, quinoids, benzoxazines, carotenoids, and alicyclics [100].Recently, anti-AChE activity of the pthalide group has also been reported, namely from a strain (No. 69-8-7-1) isolated from Rimelia reticulata, which was identified as Biscogniauxia sp., then extracted and subjected to isolation and purification to produce a new phthalide derivative, biscogniphthalides A-D (compounds 50-53), together with a known compound, [4-[(acetyloxy)methyl]-7-methoxy-6-methyl-1(3H)-isobenzofuranone (49) [9].The bioactivity of phthalide was evaluated via an anti-AChE activity test.Results from tests 49, 50, and 51 indicated weak inhibition at a concentration of 100 µM when compared to hurperzena-A, used as a positive control, which showed substantial inhibition of 87.66 ± 0.26% [9].In addition, the anti-AD activities of compounds isolated from Lichen Usnea Mutabilis Stirt were also evaluated by the AD fly model, with memantine as the positive control.In this model, transgenic AD flies carry the human Aβ 42 gene, which causes expression of the Aβ 42 peptide in the fly brain and induces AD pathological phenotypes.The results suggest the potential of these compounds as anti-AD drugs [21].

Conclusions and Future Prospects
Secondary metabolites were produced from Biscogniauxia, resulting in the isolation of 115 chemical compounds belonging to the class of secondary metabolites and fatty acids from approximately 9 taxa.The most frequently isolated chemical compounds were in the terpenoid group and the derivatives, with 43 compounds, followed by the coumarin group with 21 compounds.The use of PDA media was the largest amount, namely 75% of the total metabolite compounds produced from Biscogniauxia.Secondary metabolites of the Biscogniauxia strain have various applications in pharmacology.Many studies were also conducted to confirm associated biological activities, such as antifungal, antimycobacterial, cytotoxic activity, antioxidant, anti-germinative, phytotoxic activity, and the presence of inhibitory activity.GSK-3β enzymes, anti-AChE activity, and anti-AD effect the importance of these resources in supporting the discovery of new drugs produced by Biscogniauxia, with the potential for further development.

Table 1 .
List of secondary metabolites produced by Biscogniauxia collected from the literature.

Table 2 .
Occurrence of secondary metabolites in Biscogniauxia strain and biological activities studied.